With few foreclosed homes left to pick up on the cheap, the biggest landlords are buying, or building, new single-family homes to pad their portfolios; mortgages on these properties could show up as collateral in rental bonds.

A group led by the National Fair Housing Alliance is suing Deutsche Bank, Ocwen Financial Corp. and Altisource Portfolio Solutions, alleging real estate owned properties in minority communities do not receive the same level of upkeep and maintenance as REO houses in white neighborhoods.